Texas Parks & Wildlife wages war on invading zebra mussels

First discovered in Lake Texoma in April 2009, the fingernail-sized bivalves propagate rapidly and play havoc with their surrounding environment, clogging pipes, covering boat bottoms and ultimately threatening other aquatic life including game fish.

An unprecedented week-long effort on the part of 32 TPWD Inland Fisheries Division personnel to draw the line on the spread of zebra mussels in Texas ended at 4:30 p.m. Sept. 24, with a final dosage of potassium chloride in Sister Grove Creek. The stream flows through Grayson and Collin counties and empties in Lake Lavon, which so far is clear of the invasives.

Coordinated by Waco-based regional Fisheries director Brian Van Zee, the operation focused on killing what is believed a relatively small population of zebra mussels along the 30-mile creek, which carries water piped from Lake Texoma by the North Texas Municipal Water District into Lake Lavon.

"If we don’t stop them before they get to Lake Lavon, the whole Trinity River basin is at risk," Van Zee said.

Some 423 bags of potassium chloride — 21,150 pounds — went into the creek one plastic coffee can full at a time on an around-the-clock basis to maintain a dosage level that while hopefully fatal to zebra mussels would not be injurious to other species. TPWD staffers worked 12-hour shifts, dosing the creek from eight pre-selected points every 15 minutes.

TPWD staff, working with the U.S. Fish and Wildlife Service (which provided some funding), had been planning the operation for months. TPWD worked with the Texas Department of Agriculture to obtain the necessary permits from the US Environmental Protection Agency as well as the Texas Commission on Environmental Quality before being able to chemically treat the creek, which flows into Lake Lavon.

"We’re waiting on more data, but we have already found some [zebra mussel] mortality at a couple of points along the creek," Van Zee says. "Right now I’m cautiously optimistic."

Potassium chloride had been successfully used by the Virginia Department of Game and Inland Fisheries to kill zebra mussels found in a water-filled quarry in that state, but as far as is known the chemical has never been used to treat for zebra mussels in a flowing body of water.

"We know this common chemical, which is often used in water softeners, will kill zebra mussels," Van Zee said. "Unfortunately, it wouldn’t work in Lake Texoma because its too large of a water body and the zebra mussel population is too strong".

Texas boaters who operate their craft on Lake Texoma can do their part from keeping this harmful species from spreading by 1) cleaning any mussels, vegetation or foreign objects from the bottom of their boats; 2) draining all water from the boat, motor, livewells and bait buckets; and 3) drying the boat and trailer for at least a week before launching in another water body.

"Boaters who use Lake Texoma should wash their boats and trailers at a commercial car wash using hot, soapy water or allow their boat and trailer to dry for at least a week to prevent zebra mussels from spreading beyond Lake Texoma," Van Zee said.

For more information on zebra mussels and other invasive species see the texasinvasives.org website.